This study was carried out to investigate the types of error made by students of second semester of English Language Education STAIN Mandailing Natal and what causes of student‟s grammatical errors in short essay writing. The purpose of this study was to find out the common types of error in writing short essay paragraph. The method used in this study was qualitative. The qualitative design applied in this study was a case study. Furthermore, the subject of this study was second semester students. The writer took 24 students as the participant. The data were collected through students‟ task. The result of the error analysis process showed that students committed error into four types: omission, addition, selection, and ordering. From the frequency of each error types, selection was the error which most frequently produced by the students. It took 61.4% of the total errors. Moreover, 24.4% errors fell into error of omission and 6.8% errors fell into addition; where as, for mis-ordering, it only took 7.2%. The cause of error, there are carelessness, first language and translation.